The present invention relates to an apparatus for supporting a sliding door, which serves to open and close an entrance in the flank of the body of a vehicle, on the vehicle body, and more particularly, to a sliding door supporting apparatus provided with means for restraining the sliding door in a fully open state from being dislocated in various directions.
In many vehicles, such as one-box-cars, station wagons, etc., in particular, an opening as an entrance for users is formed in a side wall of their body, and a sliding door is used to open and close the opening. A sliding door supporting apparatus for supporting the sliding door of this type comprises upper and lower guide mechanisms, attached to the upper and lower parts, respectively, of the entrance, and a center guide mechanism attached to the vertical middle part of an outer wall at the rear portion of the vehicle body.
Usually, these guide mechanisms include upper, center, and lower rails attached to the vehicle body and rollers on the sliding door. Each roller engages its corresponding rail so as to be rollable thereon.
In this case, the upper, center, and lower guide mechanisms support the load of the door in positions of rolling contact between the guide rails and the rollers. Accordingly, the center of gravity of the door is situated within a region surrounded by line segments that connect the upper, center, and lower rolling contact positions. This positional relationship never changes even though the door moves from its fully closed position to its fully open position. Thus, the sliding door supporting apparatus of this type can support the sliding door substantially steadily on the vehicle body. According to the supporting apparatus in which all the rails are provided on the vehicle body in the aforesaid manner, however, the center rail is attached to the outer wall at the rear portion of the vehicle body, so that the external appearance of the vehicle body is poor. There is a known sliding door supporting apparatus in which the center rail is provided on the door side, thereby solving this problem.
In a sliding door supporting apparatus shown in FIGS. 25 and 26, for example, an upper rail 3 and a lower rail 4 are attached to the upper and lower parts, respectively, of a side opening 2 of a vehicle body 1. Also, a center rail 6 is attached to the inner surface of a sliding door 5. The door 5 is provided with upper and lower rollers 7 and 8, which engage the upper and lower rails 3 and 4, respectively. A center roller 9 that engages the center rail 6 is provided on the vehicle body side.
In the sliding door supporting apparatus constructed in this manner, the door load is supported in positions p1, p3 and p2 of rolling contact between the guide rails 3, 4 and 6 and the rollers 7, 8 and 9. The upper and lower contact positions p1 and p3, among these rolling contact positions, move rearward in the longitudinal direction X of the vehicle body as the sliding door 5 is moved to the fully open position. Despite the movement of the door 5 to the fully open position, on the other hand, the center rolling contact position p2 never substantially moves in the longitudinal direction X.
Thus, when the sliding door 5 is in the fully closed position, as shown in FIG. 25, the upper and lower rolling contact positions p1 and p3 are situated at a distance L1 from the center rolling contact position p2 with respect to the longitudinal direction X. In this case, the center of gravity G of the door 5 is situated substantially on the center of a region surrounded by line segments that connect the three rolling contact positions p1, p2 and p3, so that the door 5 can be supported with stability.
When the sliding door 5 is moved to the fully open position, as shown in FIG. 26, a center check member 10 and an upper check member 13 on the door side engage strikers 12 and 14 on the vehicle body side, respectively, thereby holding the door 5 in the fully open position. As this is done, the upper and lower rolling contact positions p1 and p3 approach the center rolling contact position p2 with respect to the longitudinal direction X, so that the distance L1' between the contact positions is considerably shorter than the distance L1 for the case where the door is fully closed (L1'&lt;L1). Inevitably, therefore, the three rolling contact positions p1, p2 and p3 are concentrated on the front portion of the sliding door 5. Thus, the center of gravity G of the door 5 is situated behind the positions p1, p2 and p3, so that the door 5 is liable to be dislocated in its vertical direction A, longitudinal direction X, and transverse direction (perpendicular to the drawing plane of FIG. 26).
A sliding door supporting apparatus described in Jpn. UM Appln. KOKOKU Publication No. 50-1229 is provided with a narrower second center rail on the outer wall of the vehicle body, besides the center rail on the sliding door. When the door is fully closed, according to this supporting apparatus, it is supported in the position of rolling contact between the first center rail and its corresponding roller. When the door is fully open, it is supported in the position of rolling contact between the second center rail and its corresponding roller. In this manner, the sliding door can be restrained in some measure from being dislocated in the vertical and transverse directions.
According to the arrangement described in Jpn. UM Appln. KOKOKU Publication No. 50-1229, however, the second center rail must be provided on the outer wall of the vehicle body, so that the external appearance of the vehicle body is marred inevitably. In order to allow the sliding door to move smoothly in the longitudinal direction, moreover, a gap with some width must be secured between the second center rail and the roller. The presence of the gap causes the door to be dislocated in the vertical and transverse directions. Moreover, this sliding door supporting apparatus cannot restrain the sliding door from being dislocated in the
As shown in FIG. 26, for example, means for restraining longitudinal dislocation of the sliding door in the fully open position includes the center and upper check members 10 and 13 on the sliding door 5 and the strikers 12 and 14 on the vehicle body side, which can engage the members 10 and 13, respectively. This arrangement is described in Jpn. UM Appln. KOKOKU Publication No. 7-51386 (or Jpn. UM Appln. KOKAI Publication No. 3-13220). This conventional sliding door supporting apparatus comprises a center rail attached to the sliding door, a roller attached to the vehicle body and in rolling contact with the center rail, a check member attached to the door, etc. A part of a shaft for supporting the center roller is used as the striker. This striker and the check member constitutes a check mechanism. In this prior art supporting apparatus, however, the check mechanism is provided only on the vertical middle part of the sliding door, so that it is difficult to securely restrain the door from being dislocated in various directions.
The sliding door supporting apparatus shown in FIGS. 25 and 26 comprises a center check mechanism, including the center check member 10 and the striker 12, and an upper check mechanism, including the upper check member 13 and the striker 14, in order to restrain the sliding door 5 in the fully open position from being dislocated in the vertical and longitudinal directions A and X. However, these check mechanisms are situated at a relatively long distance from the lower end portion of the door 5 that is liable to be dislocated to the highest degree, so that the door 5 may not be able to be securely restrained from being dislocated in the vertical and longitudinal directions A and X, in some cases. Moreover, it is difficult to securely restrain the dislocation of the sliding door 5, especially the rear end portion thereof, in the transverse direction (perpendicular to the drawing plane).
Thus, the sliding door supporting apparatus having its center rail on the door side cannot easily support the sliding door in the fully open position with stability. Accordingly, there has been a demand that the dislocation of the sliding door (relative to the vehicle body) be restrained more securely by steadily supporting the door in the fully open state.